1. Technical Field
The present invention relates to a robot.
2. Related Art
A multi-axis robot that includes a base and a plurality of rotatable arms and that works freely in a three-dimensional space has a problem in that vibration is easily generated in the arms due to the rotation of the arms or the disturbance applied to the arms. For the purpose of attenuating the problems of vibration, a known robot includes a vibration suppressing control technique using acceleration sensors that are provided on an arm closest to the tip side and detect acceleration in the directions of three axes including the X-axis, the Y-axis, and the Z-axis (for example, refer to JP-A-10-100085). Another known multi-axis robot includes a base and a plurality of arms and has the rotation axes of the arms parallel to each other and provides angular velocity sensors on the arms, respectively, and is controlled by calculations that also include the components detected using the angular velocity sensors (for example, refer to JP-A-2005-242794).
However, the robots described in JP-A-10-100085 and JP-A-2005-242794 have the following drawbacks.
In the robot of JP-A-10-100085, the acceleration sensor is installed at the tip portion of the arm link portion closest to the tip side. Thus, the acceleration detected by the acceleration sensor is converted and corrected into those for the respective joint portions. At this time, since it is necessary to perform a coordinate axis transformation referred to as the Jacobi's transformation, and a matrix calculation having a number of sine and cosine factors is required, the amount of calculations becomes huge. Since it is necessary to calculate the factors according to the rotation angles of the motors of the respective joint portions that change every moment, it is always necessary to execute huge calculations. Accordingly, there is a drawback in that the response speed becomes slow.
Additionally, since accurate acceleration or speed cannot be fed back if calculation precision declines, vibration suppression capability may decline or control performance may be impaired. For this reason, there is a restriction on the design of a control system such that a high-speed computing unit is required, for example.
Additionally, in the calculation of the coordinate axis transformation, there is a region (incalculable region) with no coordinate axis transformation solution referred to as a singular point. In this region, the vibration suppression capability may decline or vibration may be increased instead.
In the robot of JP-A-2005-242794, since the rotation axes of the arms are parallel to each other and the directions of the components detected by the angular velocity sensors are the same, a calculation and control method in which different rotational components are mixed are not taken into consideration. Accordingly, even if this technique is adopted for a multi-axis robot in which the rotation axes of the arms are different from each other, vibration suppression capability cannot be satisfied.